Constitutive NOS uncoupling and NADPH oxidase upregulation in the penis of type 2 diabetic men with erectile dysfunction

Abstract

Erectile dysfunction (ED) associated with type 2 diabetes mellitus (T2DM) involves dysfunctional nitric oxide (NO) signaling and increased oxidative stress in the penis. However, the mechanisms of endothelial NO synthase (eNOS) and neuronal NO synthase (nNOS) dysregulation, and the sources of oxidative stress, are not well defined, particularly at the human level. The objective of this study was to define whether uncoupled eNOS and nNOS, and NADPH oxidase upregulation, contribute to the pathogenesis of ED in T2DM men. Penile erectile tissue was obtained from 9 T2DM patients with ED who underwent penile prosthesis surgery for ED, and from 6 control patients without T2DM or ED who underwent penectomy for penile cancer. The dimer-to-monomer protein expression ratio, an indicator of uncoupling for both eNOS and nNOS, total protein expressions of eNOS and nNOS, as well as protein expressions of NADPH oxidase catalytic subunit gp91phox (an enzymatic source of oxidative stress) and 4-hydroxy-2-nonenal [4-HNE] and nitrotyrosine (markers of oxidative stress) were measured by Western blot in this tissue. In the erectile tissue of T2DM men, eNOS and nNOS uncoupling and protein expressions of NADPH oxidase subunit gp91phox, 4-HNE- and nitrotyrosine-modified proteins were significantly (p<0.05) increased compared to control values. Total eNOS and nNOS protein expressions were not significantly different between the groups. In conclusion, mechanisms of T2DM-associated ED in the human penis may involve uncoupled eNOS and nNOS and NADPH oxidase upregulation. Our description of molecular factors contributing to the pathogenesis of T2DM-associated ED at the human level is relevant for advancing clinically therapeutic approaches to restore erectile function in T2DM patients.

Icariin improves SHR erectile function via inhibiting eNOS uncoupling

“…In addition to phosphorylation of eNOS, the maintenance of eNOS in the coupling state is also critical for eNOS to exhibit bioactivity (Musicki & Burnett, ). Studies found that decrease in BH4 and uncoupling of eNOS was the causes of NO decrease in hypertensive aortic tissues (Landmesser et al, ).…”

“…After washing again, ECL chemiluminescence was added to the sample in the dark. In conclusion, the membrane was placed into a gel imager for imaging (Musicki & Burnett, ; Yamamoto, et al, ). GAPDH was used as the internal reference.…”

Phosphodiesterase type 5 in men with vasculogenic and post‐radical prostatectomy erectile dysfunction: is there a molecular difference?

“…Penile tissue was homogenized as reported previously . NO synthases (NOSs) were partially purified as described previously .…”

“…Penile tissue was homogenized as reported previously . NO synthases (NOSs) were partially purified as described previously . Membranes with partially purified NOSs were probed with anti‐phospho‐neuronal (n)NOS (Ser‐1412) antibody (polyclonal rabbit, kindly provided by Dr Solomon Snyder, Johns Hopkins University, Baltimore, MD, USA) at 1:6 000 dilution or anti‐phospho‐endothelial (e)NOS (Ser‐1177) antibody (polyclonal rabbit; Cell Signaling Technology, Beverly, MA, USA) at 1:450 dilution (for phospho‐nNOS and phospho‐eNOS analyses) .…”

Re: Role of endothelin receptors and relationship with nitric oxide synthase in impaired erectile response in diabetic rats. Alkan E, Ugan RA, Basar MM, Halici Z, Karakus E, Balbay MD, Un H.Andrologia. 2016 May 4. doi: 10.1111/and.12607

“…Recent studies have shown that increased oxidative stress and NOS uncoupling are accepted as a mechanistic link between erectile dysfunction and systemic endothelial dysfunction in type DM (Musicki & Burnett, 2017;Musicki, Hannan, Lagoda, Bivalacqua, & Burnett, 2016). But NOS uncoupling and penile ROS levels have not been evaluated in this study.…”